| Message ID | CA+jPhpfu9wB3UTPSepNRVODAwmQ1=W2UrO+xE5GeBRW4cfKp8g@mail.gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | Fixes for LP1800849 [v2] | expand |
On 02.11.18 20:13, Frank Heimes wrote: > From: Claudio Imbrenda <imbrenda@linux.vnet.ibm.com > <mailto:imbrenda@linux.vnet.ibm.com>> > > BugLink: http://bugs.launchpad.net/bugs/1800849 > > When the oom killer kills a userspace process in the page fault handler > while in guest context, the fault handler fails to release the mm_sem > if the FAULT_FLAG_RETRY_NOWAIT option is set. This leads to a deadlock > when tearing down the mm when the process terminates. This bug can only > happen when pfault is enabled, so only KVM clients are affected. > > The problem arises in the rare cases in which handle_mm_fault does not > release the mm_sem. This patch fixes the issue by manually releasing > the mm_sem when needed. > > Fixes: 24eb3a824c4f3 ("KVM: s390: Add FAULT_FLAG_RETRY_NOWAIT for guest fault") > Cc: <stable@vger.kernel.org <mailto:stable@vger.kernel.org>> # 3.15+ > Signed-off-by: Claudio Imbrenda <imbrenda@linux.vnet.ibm.com > <mailto:imbrenda@linux.vnet.ibm.com>> > Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com > <mailto:schwidefsky@de.ibm.com>> > (cherry picked from commit 306d6c49ac9ded11114cb53b0925da52f2c2ada1) > Signed-off-by: Frank Heimes <frank.heimes@canonical.com > <mailto:frank.heimes@canonical.com>> Acked-by: Stefan Bader <stefan.bader@canonical.com> > > --- Possibly needs real cherry pick if this multi-part html thing cannot be seperated away. > > diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c > index e074480..4cc3f06 100644 > --- a/arch/s390/mm/fault.c > +++ b/arch/s390/mm/fault.c > @@ -502,6 +502,8 @@ static inline int do_exception(struct pt_regs *regs, int access) > /* No reason to continue if interrupted by SIGKILL. */ > if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) { > fault = VM_FAULT_SIGNAL; > + if (flags & FAULT_FLAG_RETRY_NOWAIT) > + goto out_up; > goto out; > } > if (unlikely(fault & VM_FAULT_ERROR)) > >
diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c index e074480..4cc3f06 100644 --- a/arch/s390/mm/fault.c +++ b/arch/s390/mm/fault.c @@ -502,6 +502,8 @@ static inline int do_exception(struct pt_regs *regs, int access) /* No reason to continue if interrupted by SIGKILL. */ if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) { fault = VM_FAULT_SIGNAL; + if (flags & FAULT_FLAG_RETRY_NOWAIT) + goto out_up; goto out; }